Design and optimization of the mining method of boundary coal-pillars with high recovery ratio and high efficiency

Based on the simplified plane shape, a new mining design and optimization method for recovering boundary coal-pillars, called arc-face mining method, was presented. Its advantages are as follows:easy to choose the related comprehensive auxiliary equipment, high recovery ratio and efficiency, and fitting the fully mechanized coal mining technology, even the sub-level longwall eaving face technology when the geologic condition is permitted. The key techniques include:developing a series of underground chambers along tailgate; in a chamber, storing some supports which will be added to the coming face-supports when the face advances near the chamber; canceling face-end supports and adopting a simple conveyer in order to add or remove supports quickly. Then, with the linear mathematics programming theory, the objective function of recovery efficiency and the constraint functions of safety and exploitation cost were established. It is concluded that the increased number of supports each time not only affects the number of underground chambers but also the efficiency. The optimization analysis also provides various optimal technology schemes with the principle of higher efficiency or lower cost.